The present invention relates to methods or devices for encoding structured documents, particularly XML documents, in which a bit stream is generated from a structured document as a function of a schema, and a method or device for decoding, in which a structured document is generated from a bit stream as a function of a schema.
In the context of the work on the MPEG-7 standard, a method for binary encoding of XML data was developed which is referred to as the BiM method in the following and which is known, for example, from the publication ISO/IEC FDIS 15938-1:2001(E), “Information Technology—Multimedia Content Description Interface—Part 1: Systems.” This method uses XML schema definitions which are available at the encoder and the decoder, such as the MPEG-7 schema, in order to generate the codes for the individual data elements of the XML description. A precondition for this method is that the same schema definitions are available at least in part to the encoder and the decoder. This can be ensured, for example, if a standardized XML schema is permanently installed in the decoder. Moreover, the possibility exists of transferring the schema to the decoder separately or in addition to the actual document. The transmission of the schema from the encoder to the decoder can be carried out in textual form, where standard text compression, such as ZIP, can be applied.
The present invention is directed toward specifying methods or devices in such a way that the transmission of the schema is carried out particularly efficiently and the dataset transmitted and the computing performance at the decoder, which is needed for generating the code tables from the schema, is reduced. Moreover, the consistency of a schema which has not been transmitted in full should be ensured.